Polyhydroxyalkanoate (PHA) Bio-polyesters – Circular Materials for Sustainable Development and Growth

A. Mukherjee and M. Koller

Abstract
The need for circularity of the carbon in the life of materials calls for fundamental changes in the way polymers are currently produced. Functional materials starting from truly renewable feedstock, which does not conflict with food and animal feed, until their biodegradation under diverse environmental conditions as the desired end-of-life option indeed constitutes a paradigm shift in plastics industry. Considering the ever-increasing environmental problems associated with the disposal or incineration of fossil plastics, such as increasing microplastic formation, food contamination, and rising atmospheric CO2 concentrations, it becomes clear that now the time is ripe for alternative, innovative, and sustainable polymers with plastic-like properties. In this nexus, the present review shines new light on the benefits of biobased and, at the same time, biodegradable microbial polyhydroxyalkanoate (PHA) biopolyesters. Special emphasis is dedicated to carbon recyclability through biodegradability and compostability aspects of these fascinating natural biopolymers, which are slowly but steadily being commercialized as replacement for fossil-based chemical thermoplastics and elastomers produced and disposed on an annual multi-million-ton scale, resulting in a growing environmental threat. It is shown that end-of-life options of PHA are analogous or even superior to those of other well-known polymers from nature, such as cellulose or poly(lactic acid), while PHA offer the additional benefit of acting as “bioplastics” with tailor-made properties. Finally, it is demonstrated how PHA biopolyesters can even contribute to reaching some of the heavily discussed and desired UN Sustainable Development Goals.

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Keywords
biopolymers, biodegradable polymers, circular bioeconomy, circular materials, microbial biopolyesters, microplastics, polyhydroxyalkanoate, UN Sustainable Development goals